Fluid level alarm and control device

ABSTRACT

A gas operated audible alarm device is provided to signal the advent of an overflow or leakage condition in oil tanks and the like to minimize the hazards of environmental pollution from oil and chemical spills during tank filling operations. The device has a float operated pneumatic valve positioned at a predetermined upper limit of fluid level in a receiving tank, which valve controls the passage of an inert gas from a supply source to a gas operated whistle or horn in response to an overflow or leakage condition sensed by the float. In one embodiment the alarm device may be placed in the rakes of a barge or the bilge of a ship to sound an alarm in response to a sinking condition of the ship or barge. In another embodiment the source of gas is connected in circuit with a pressure sensitive switch which will actuate means to shut down the supply of oil in response to an overflow or leakage condition sensed in the oil tanks being filled.

United States Patent 1191 7 Ward et al.

[ 1 FLUID LEVEL ALARM AND CONTROL DEVICE [76] Inventors: John T. Ward,6279 W. Rockburn Hill, Elkridge, Md. 21227; Allen B.

Keller, 2914 Ontario Ave., Baltimore, Md. 21234 [22] Filed: Nov. 27,1973 [2]] Appl. No.: 419,362

Related US. Application Data [62] Division of Ser. No. 370,548, June 15,1973, Pat. No.

[52] U.S. C1 116/110, 73/307, 73/319, 116/112, 137/558, 417/40 [51] Int.Cl. G011 23/00 [58] Field of Search 73/305, 307, 308, 309,

[56] References Cited UNITED STATES PATENTS 291,272 l/l884 Bate 137/429X 1,484,144 2/1924 Marsh 116/110 1,653,996 12/1927 Estep 137/434 X1,898,546 2/1933 Kellet ll6/ll2- 2,233,229 2/1941 Tapp 116/110 X 12/1962Buell, Jr. et al. 116/112 111' 3,857,359 [451 Dec. 31, 1974 3,347,09710/1967 Collins'et a1 116/118 X 3,675,614 7/1972 Ward et al. 116/1183,807,899 4/1974 Ward et al. 417/40 Primary Examiner-Louis .1. CapoziAttorney, Agent, or Firm- Herbert M. Birch; Terrell C. Birch; Anthony L.Birch 57 ABSTRACT A gas operated audible alarm device is provided tosignal the advent of an overflow or leakage condition in oil tanks andthe like to minimize the hazards of environmental pollution from oilandchemical spills during tank filling operations. The device has afloat operated pneumatic valve positioned at a predetermined upper limitof fluid level in a receiving tank, which valve controls the passage ofan inert gas from a supply source to a gas operated whistle or horn inresponse to an overflow or leakage condition sensed by the f1oat..1n oneembodiment the alarm device may be placed in the rakes of a barge or thebilge of a ship to sound an alarm in response to a sinking condition ofthe ship or barge. In another embodiment the source of gas is connectedin circuit with a pressure sensitive switch which will actuate means toshut down the supply of oil in response to an overflow or leakagecondition sensed in the oil tanks being filled.

21 Claims, 9 Drawing Figures N 2 SUPPLY PATENTED M11 1 I914 3', 857, 359

SHEET 1 [IF 4 7 1 I N2 SUPPLY 247 N 2 SUPPLY ll/l/ll/f/l/l/ PATENTEUDEC31 I974 sums or 1 PATENTEDBEE31 I974 SHEET u 0F 4 u vw I llillll IIIqwfl FLUID LEVEL ALARM AND CONTROL DEVICE This is a division ofapplication Ser. No. 370,548 filed June 15, 1973 now U.S. Pat. No.3,807,899.

BACKGROUND OF INVENTION The present invention is an improvement over US.Pat. No. 3,675,614 issued July ll, 1972 to the same inventors of thepresent invention. it is intended to incorporate by reference thedisclosure of said U.S. patent herein.

FIELD OF INVENTION This invention relates to an audible alarm andcontrol means for sensing the level of a liquid or fluid. Moreparticularly the present invention relates to an audible alarm andcontrol means for sensing the level of fluid in oil tanks or the bilgeor rakes of a ship, which sound an alarm or performs a control functionin response to an undesirable fluid level which is sensed.

DESCRIPTION OF PRIOR ART Many spills of oil and other undesirablesubstances which pollute the environment are occasioned by human error.One of the most' common forms of human error is the failure to detectthat the fluid level in a tank being filled with oil or other fluidchemicals is immediately proximate to the overflow point of the tank.

Attempts have been made in the prior art to provide float actuated orpressure actuated audible alarm devices which provide an indication ofthe advent of an overflow condition in a storage tank. Such storagetanks may be fixed or ambulatory land-based tanks or located on cargobarges or other vessels.

Due to the highly flammable and/or reactive nature of many fluidscontained in such storage tanks, electrical alarm systems are undulyexpensive since theymust be both corrosion resistant and spark free.Furthermore, alarm systems utilizing compressed air and compressedcarbon dioxide as the activating medium for an audible whistle orsimilar device have numerous drawbacks based upon environmental problemssuch as freezing or unsafe reactions with the fluids contained in thetanks being monitored by the alarm devices.

OBJECTS OF INVENTION It is, therefore. an object of the presentinvention to provide a new and novel audible alarm device for indicatingthe advent of an overflow fluid level in storage or cargo tanks which isfoolproof in operation and has optimum environmental capabilitiesregarding both the internal and external environments of the tank beingmonitored.

Another object of the present invention is to provide a new and novelaudible alarm device having an optimally minimum number of working partsand optimally minimum downtime due to service problems.

Still another object of the present invention is to provide a new andnovel audible alarm device and system for a plurality. of such devicesshaving a source of pressurized actuating fluid feeding each of aplurality of such audible alarm devices whereby an entire network ofcargo or storage tanks can be successfully monitored to indicate theadvent of overflow conditions in any given tank.

It is a further object of the present invention to provide an audiblealarm device which can detect either a leakage condition in a tank inresponse to the fluid level falling below a predetermined minimum or anoverflow condition in response to the fluid level in said tank exceedinga predetermined maximum.

It is still a further object of the present invention to provide anaudible alarm device which is more compactthan prior art devices andmore reliable in its operation.

It is another object of the present invention to provide an audiblealarm device which is suitable for sensing a sinking condition of a shipor barge.

It is yet another object of the present invention to provide anautomatic control means for shutting down a tank filling operation inresponse to the same undesirable fluid level conditions which wouldgeneratean alarm signal.

These and other objects of the invention will become more fully apparentwith reference to the following specification and drawings which relateto a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a top plan view of an audible alarm device of the presentinvention and a portion of asystem embodying same;

FIG. 2 is a perspective view of the audible alarm device of FIG. 1; I

FIG. 3 is a side elevational view of the audible alarm device and'portion of the system illustrated in FIG. 1

' mounted in a suitable tank;

. FIG. 4 is a top plan view of an audible alarm system of the presentinvention mounted on a ship or barge;

FIG. 5 is a side elevational view of the system of FIG.

FIG. 6 is a schematic view of the automatic control means of the presentinvention for automatically shutting down the filling operation of anoil barge;

FIG. 7 is another embodiment of the audible alarm device of the presentinvention which detects either an overflow or leakage condition in atank;

FIG. 8 is atop plan view of the alarm device of FIG. 7; and

FIG. 9 is a front elevational view of the alarm device of FIG. 7.

Basically, the invention comprises a float actuated valveinterconnecting a source of dry nitrogen gasunder pressure through thesaid valve to a whistle or horn device adapted to be actuated by gasunder pressure. The alarm device is adapted to be positioned in theupper extremities of the interior of a cargo or storage tank whereuponthe float is responsive to the liquid level in the cargo or storage tankto actuate the valve and release nitrogen under pressure to the whistlewhen the level in the tank approaches an overflow condition. If amultiplicity of tanks is involved, each tank is provided with anindividual audible alarm device connected to a supply header or manifoldwhich in turn is connected to. a source of pressurized dry nitrogen todrive the individual whistles on the audible alarm devices when thefluid level in any given tank approaches an overflow condition.

In another embodiment of the present invention an alarm device isprovided including means for sounding said alarm in response to eitheran overflow condition or leakage condition in a cargo or storage tank.This is facilitated by including mechanical linkage means both above andbelow the float, both of said linkage means being coupled to the floatactuated valve, for actuating said valve in response to either anoverflow condition,

wherein the fluid in said tank exceeds a predetermined level, or aleakage condition, wherein the fluid in said tank falls below apredetermined minimum.

In yet another embodiment of the invention the alarm device can beplaced in the rakes or bilge of a ship to sound an alarm in response toa sinking condition of said ship.

In still another embodiment of the present invention the alarm devicesof the present invention may be modified to generate an automaticcontrol signal. For example the dry nitrogen gas under pressure which isreleased in response to a predetermined condition may simultaneously beused to actuate a pressure responsive control switch in response to saidcondition. In a preferred embodiment said pressure responsive controlswitch is adapted to actuate an electromagnetic control valve in thesupply line of an oil pumping system located on a land based loadingdock and a relay in the electrical circuit of the pumping system.Therefore, when an overflow, leakage, or other undesirable condition issensedby'said alarm device, said pressure responsive switch willgenerate a control signal to said electromagnetic control valve andrelay in said pumping system, which automatically shuts down the supplyof oil being pumped from said loading dock. This embodiment constitutesa significant advance in the art sincean automatic shut down of thepumping operation occurs substantiallysimultaneously with the soundingof the alarm.

Referring in detail to the drawings and more particularly to FIGS. 1, 2and 3, the audible alarm device of the present invention is shown ascomprising a main mounting bracket 12 attached to an open frame 14constituting of struts l1 and support ring 18. Extended from the openframe is a float constraining cage device 16 which is defined at anupper end by ring 18, a plurality of dependent struts 20, welded orotherwise fixed to the upper support ring 18, and a circular bottomplate 22, welded or otherwise fixed to the lower end of the verticalstruts 20. The vertical struts 20 are substantially of identical lengthsuch that the lower support plate 22 is substantially parallel to theplane of the upper support ring 18.

A spherical float 24 is rigidly affixed to foot 368 of bell crank 36 bywelding or other suitable means within float cage 16 and normally seatson the lower support plate 22 so long as the level of the fluid inthetank being monitored is below the lower support plate 22.

Mounted in the box frame 14, through the bracket 12, is a valve assembly26. The valve assembly 26 includes a plunger operated on-off typepneumatic valve 28 in-line mounted in a pneumatic manifold pipe 30 whichextends from an input portion 30A through the main mounting bracket 12through-the valve 28 and thence back through the mounting bracket 12 toan output section 30B. Plunger 32 extends vertically above the valve 28in response to a predetermined liquid level in a tank in which the alarmdevice l0 is of the bell crank 36 is provided with a contact foot 36Bwhich is rigidly affixed to the spherical float24 consure through afilter 47. Filter 47 prevents foreign particles from entering anddamaging the valve seat in valve 28; prevents damage to the diaphragmsof whistles 44 by foreign particles, such as metal shavings from pipethreading, dirt or rust in the pipes; and prevents damage to theregulator valve 48 of nitrogen supply 42. See FIG. 8. As shown in FIG. 3nitrogen supply 42 is provided with a pressure regulator valve 50 havingpressure gauges 52 mounted thereon The output section 30B of thepressure manifold 30 is directly connected to a gas operated whistle 44suitably mounted on top of tank T. v

The fact that float 24 is rigidly affixed by welding or other suitablemeans to foot 368 of hell crank 36 offers distinct advantages 'over theadvible alarm device disclosed in US. Pat. No. 3,675,614 issued July 1l, 1972 to the same inventors as the present invention. In that patenteddevice float 24 was freely constrained within float cage 16 wherein thefloat 24 had to rise at least four inches before contacting foot 36B ofbell crank 36. In contradistinction the float 24 of the presentinvention is fixedly attached to foot 36B and needs only travel aboutone quarter of an inch to raise bell crank 36 a sufficient distance toopen valve 28. This reduces the overall height necessary for cage 16and, therefore,

makes the audible alarm device of the present inven-' tion more compact.The structure of the present invention is also faster acting anddecreases the probability of float 24 hanging up in cage 16, becausefloat 24 travels only one'quarter-of an inch instead of four inchesthrough cage 16 and is substantially constrained against lateralmovement.

As shown in FIG. 3 the audible alarm device 10, is' shown with the mainmounting bracket 12 affixed to mounting brackets 12A and 12B affixed tothe side wall 46 in the upper dome of tank T. The corners of mountingbracket 12 are angled instead of square. This feature in combinationwith the use of mounting brackets 12A and 12B facilitates the mountingof alarm device 10 on either a flat or rounded surface.

It is of the utmost importance that the supply of pressurized inert gasbe dry nitrogen gas in the present invention and its application. Thisis occasioned by the fact that ordinary comprssed air and many otherreadily available compressed gases would create highly flammableconditions within the tank due to their oxygen or other reactive gascontent should there be a malfunction in the valve assembly 26 or thepressure manifold 30 within the tank T.

Furthermore, a commonly available inert gas, namely, carbon dioxide, hasinherently bad qualities for alarm devices of this type due toenvironmental problems. For example, should there be an undue amount ofmoisture in the air or should the temperatures be relatively low in theatmosphere surrounding the tanks, the whistle 44, when subjected to ablast of carbon dioxide therethrough in order to sound'the alarm, wouldfreeze and preclude proper actuation.

Dry nitrogen, on the other hand, is readily available and will not.create freezing conditions when released ply of dry nitrogen in theimmediate area of ture. Neither will it react with the fluid contents ofthe tank Tto endanger life, limb and/or property due to adverse chemicalreactions or fire within the tank T.

To illustrate the effectiveness of the audible alarm device 10, forexample, if dry nitrogen under 40 pounds per square inch pressure ispermitted to energize a conventional steam or air whistle 44, noiselevels of at least 99 decibels or greater can be produced. This issufficient for industrial applications or other high noise levelenvironments.

In a preferred embodiment for the prevention of oil spills from storageand cargo tanks the spherical float 24 can be constructed from copperand dimensioned to be -inches in diameter, thereby providingapproximately pounds of lift in response to an overly high fluid levelin the tank T. The mounting bracket 12, open frame 14 and the float cage16 can be constructed of stainless steel and the air valve 26 can be astandard bronze air valve. The use of half-inch heavy duty galvanizedpneumatic lines for the manifold 30 and the main supply header 40 isalso contemplated.

In operation, referring to FIGS. 1, 2 and 3, the audible alarm device 10is mounted in the tank T such that a liquid level Ll (indicated by thelowermost dotted line position in the tank T to FIG. 3) or less willhave no effect on the audible alarm device 10. However, when the liquidlevel reaches the level L2 (indicated by the uppermost dotted lineposition in the tank T in FIG. 3) the spherical float 24 will beconstrained to assume the dotted line position shown in FIG. 2. Thiscauses the float 24 to direct an upward force against the foot 368 onthe bell crank 36 forcing the said bell crank 36 to pivot about thepoint 38 and force the contact foot 36A down against the plunger 32 ofthe air valve 28. The resulting depression of the plunger 32 opens thenormally closed air valve 28 and permits pressure from the supply header40 and supply 42 to flow into the inlet portion 30A of the pressuremanifold 30 and through the valve 28, out through the outlet 30B of theheader 30 and into the gas whistle 44 to thereby sound an audible alarmindicating that the liquid level L2 has been achieved within the tank T.

Referring to FIGS. 4 and 5 there is shown a ship or barge generallydesignated 54 having four cargo tanks 56, 58, 60, and 62. An audiblealarm device 10 is disposed in a dome portion 46 of each of said tanksand similar alarm devices 10 are located in the rakes 54A and 54B ofbarge 54. Alarm devices 10 may either be the type disclosed in FIGS. 1to 3 or the type shown in FIG. 7 to be described hereinafter. A commonor central supply of nitrogen 42 is connected through supply header 40,which is connected to manifold 30 of each of the alarm devices 10. Inthe alternative a separate source of nitrogen may be provided for eachof the alarm devices 10. The use of separate sources of nitrogen isparticularly useful on ships or barges larger than 150,000 barrels. Theuse of separate sources eliminates the need for long lengths of pipe,thereby reducing the chance of leaks; increases the supply of drynitrogen available for each alarm device; and localizes the supeach tankor area being monitored.

Referring to the operation of the system disclosed in FIGS. 4 and 5 ofthe alarm devices 10 in tanks 56, 58, 60, and 62 will sound horns orwhistles 44 upon the occurrence of an overflow and/or leakage conditionin any of said tanks and alarm devices 10 in the rakes 54A and 54B ofbarge 54 will sound alarm horn or whistles 44 if the water in the rakesrises above a predetermined level commensurate with a sinking conditionof the ship. Therefore, the system of FIGS. 4 and 5 comprises a failsafe alarm system which will warn the barge crew of any condition whichmight lead to an oil spill or dangerous condition on the ship.

Referring to FIG. 6 there is shown an embodiment of the presentinvention for automatically shutting down the pumping of oil or otherfluid material from a loading dock to a barge 54. Barge 54 may be of thetype II- lustrated in FIGS. 4 and 5 having at least four oil tanks, eachof said tanks having an alarm device 10 disposed therein. 7

Each of the alarm devices 10 is connected to a common pressure switch 68by suitable conduit means 64 connected to output manifold sections 30Bof each of the respective alarm devices 10. Suitable check valves 66 maybe provided in conduits 64 to restrict the flow of nitrogen to pressureswitch 68 after the pressure builds up to a sufficient level to triggerswitch 68.

Pressure switch 68 may be any suitable commercially available type whichgenerates an electrical output pulse or signal in response to a fluericor fluidic input signal. The output of pressure switch 68 is connectedthrough electrical cable 70 to electrical connector 73 of the electricalsystem of the pumping means located on loading clock 53. An electricalcable 72 extends between electrical connector 73 and a relay (not shown)which turns the power on and off to the pumping means. Said relay may belocated for example in the main pumping room on the loading dock. Anelectrical cable 71 is also provided which extends from connector 73 toan electromagnetically actuated gate valve 7 located in the main supplyline 78 of the oil pumping means. A manually operated gate valve 76 mayalso be provided in line 78. i

In operation an overflow or leakage condition in any of the tanks onbarge 54 will release nitrogen under pressure through outletmanifold-sections 30B of alarm devices 10. This nitrogen willsimultaneously be supplied to horns or whistles 44 through outletsections 30B and to pressure switch 68 through conduits 64 by way ofcheck valves 66. This will cause pressure switch 68 to generate anoutput control signal through electrical cables 70, 71, and 72 to therelay in the pump room and to electrically actuated gate valve 74. Thisoutput control signal causes the relay in the pump room to open shuttingdown the pumps and closes electrically actuated gate valve 74, whichstops the flow of oil or fluid through conduit 78 to the tanks on oilbarge 54. Simultaneously with the shutting down of the pumping operationhorns or whistles 44 are sounded warning the operator of the overflow orleakage conditions in the oil tanks being filled.

Referring to FIGS. 7 to 9 there is illustrated an alarm device forsignaling either an overflow or leakage condition in a tank T having adome portion-46 and a removable hatch 80. The alarm device of FIGS. 7 to9 is substantially identical to the alarm, device of FIGS. 1 to of thebuoyant force of supporting fluid beneath disc 84, the weight of float24 will force disc 84 downwardly along rod 82. The relative diameters ofbore 36C and rod 82 must of course be such that the vertical arm of bellcrank 36 may be moved laterally a sufficient distance with respect torod 82 to permit bell crank 36 to pivot about point 38 a sufficientamount to depress valve actuator 32. Rod 82 may be attached to the wallsof tank T by welding or any other suitable rneans.

The leakage condition-sensing means of the alarm device of FIGS. 7 to 9includes disc 84, a pulley or reel 88, a'cable 86 wound around reel 88,and a lever 90 supported about a pivot point 94. Pulley or reel 88 ispivotally mounted on lever 90 about pivot point 88B and may be adjustedthrough hatch 80 by rotating reel 88 to wind or unwind a selected amountof cable 86 and thereby adjust the height of disc 84. Reel 88 may belocked in any desired position by any' suitable means. For example theperiphery of reel 88 may contain a series of apertures 88A which may bealigned with a locking pin 90A, which passes through a suitable aperturein lever 90. A second locking pin 92 may be provided for supportinglever 90, reel 88, and disc 84 just prior to a filling operation whentank T is empty. After the fluid in tank T reaches a predeterminedminimum level which is sufficient to buoyantly support disc 84, lockingpin 92 may be removed. Locking pin 92 may be supported on a bracket 91extending from support 12 or any suitable wall of tank dome 46. Lockingpin 92 may be adjusted by reaching through the opening provided by hatch80.

Referring to the operation of the alarm device of FIGS. 7 to 9 anoverflow condition is sensedc in substantially the same manner asdescribed with respect to the alarm device of FIGS. 1 to 3. When thefluid level in tank T rises above a predetermined level L2, float 24travels up rod 82'and presses against foot 368 of bell crank 36. Thiscauses bell crank 36 to pivot about point 38 thereby depressing valveactuator 32, which opens valve 28 and releases nitrogen gas throughmanifold outlet section-30B to horn or whistle 44. If on the other handa leak occurs in tank T the fluid level in tank T will fall to apredetermined minimum level LI, the weight of .float 24 will cause disc84 to slide down rod 82 pulling on cable 86, which will cause lever90.to pivot about point 94 and depress valve actuator 32. In

a like manner to the overflow sensor this will initiate the release ofnitrogen to horn or whistle 44 to sound an alarm indicating that tank Tis leaking.

From the foregoing, it can now be readily seen that the presentinvention satisfies a long-felt need in the art to aid in precludingenvironmental pollution due to oil spills and the like.

lt should be understood that the present invention may be modified aswould occur to one of ordinary skill in the art without departing fromthe spirit and scope of the invention. i

What is claimed is:

1. An audible alarm device for detecting and signalling the advent of anoverflow condition in a fluid storage tank, comprising:

a source of dry nitrogen gas under pressure;

gas operated audible means external of said storage tank;

valve means mounted internally of said storage tank including pneumaticpressure lines interconnecting opposite sides of said valve means withsaid source and said audible means, respectively; and

float means mounted internally of said storage tank,

interconnected with said valve means, and responsive to a predeterminedfluid level representing the advent of an overflow condition in saidstorage 'tankto actuate said valve means to transmit gas from saidsource through said pneumatic lines to said audible means, said floatmeans including a float in said tank, a fluid pervious float cagecontaining said float and constraining the same to a limited verticaldisplacement in response to varying fluid levels in said tank, andlinkage means extending from said float cage to said valve means foractuating said valve means, said float rising in said float cage andengaging said linkage means in response to said predetermined fluidlevel to constrain said linkage means to actuate said valve means andeffect actuation of said audible means;

pivot means on said valve means;

an operating plunger for said valve means; and

a bell crank lever pivoted intermediate the ends thereof on said pivotmeans;

, said bell crank lever being rigidly affixed to said float on oneendthereof and means engaging said operating plunger on the other endthereof.

2. The invention defined in claim 1 including filter means connectedbetween said source of dry nitrogen gas and said pneumatic pressurelines for filtering out foreign materials from said nitrogen gas.

3. A system for detecting and signaling the advent of oil spills by aship or barge having at least one oil tank thereon comprising:

a. an alarm device including a source of dry nitrogen gas underpressure,

gas operated audible means exernal of said storage tank,

pneumatic valve means mounted internally of said storage tank includingpneumatic pressure lines interconnecting opposite sides of said valvemeans with said source and said audible means, respectively, and

float means interconnected with said valve means, and responsive topredetermined fluid levels to actuate said valve means to transmit gasfrom said source through said pneumatic lines to sound said audiblemeans;

b. means for mounting at least one of said alarm devices in said atleast one tank to constrain said float means to actuate said valve meansto transmit gas from said source through said pneumatic lines to saidaudible means in response to at leastone predetermined fluid level insaid at least one tank, and

4. The invention of claim 3 wherein one of said predetermined fluidlevels in said tank corresponds to an overflow condition in said tankand said audible means is sounded in response to said overflowcondition.

5. The invention of claim 3 wherein one of said predetermined fluidlevels in said tank corresponds to a leakage condition in said tank andsaid audible means is sounded in response to said leakage condition.

6. The invention of claim 3 wherein a first predetermined fluid level insaid tank corresponding to an overflow condition will sound said audiblemeans and a second predetermined fluid level in said tank correspondingto a leakage condition will also sound said audible means.

7. The invention defined in claim 3, wherein said float means comprises:i

a float in said tank;

a fluid pervious float cage containing said float and constraining sameto a limited vertical displacement in response to varying fluid levelsin said tank; and

linkage means extending from said float cage to said valve means foractuating said valve means, said float rising in said float cage andengaging said linkage means in response to said predetermined fluidlevel to constrain said linkage means to actuate said valve means andeffect the sounding of said audible means.

8. The invention defined in claim 7, wherein said valve means isnormally closed and said linkage means comprises:

pivot means on said valve means:

an operating plunger for said valve means; and

a bell crank lever pivoted intermediate the ends thereof on said pivotmeans;

said bell crank lever being rigidly affixed to said float on one endthereof and means engaging said operating plunger on the other endthereof.

9. The invention of claim 3 wherein said float means comprises:

a float in said tank mounted for slidable movement on vertical rod meansin response to varying fluid levels in said tank;

first and second linkage means extending from said rod means to saidvalve means for actuating said valve means, said float rising along saidrod means and engaging said first linkage means to actuate said valvemeans and sound said audible means in response to a first fluid levelcorresponding to an overflow condition in said tank, said float movingdown said rod means and engaging said second linkage means to actuatesaid valve means and sound said audible means in response to a secondfluid level corresponding to a leakage condition in said tank.

10. The invention of claim 9' wherein said valve means is normallyclosed and said first linkage means comprises:

pivot means on said valve means;

an operating plunger for said valve means; and

a bell crank lever pivoted intermediate the ends thereof on said pivotmeans;

said bell crank lever having means for engaging said float on one endthereof and means engaging said operating plunger on the other endthereof.

11. The invention of claim 9 wherein said valve means is normally closedand said second linkage means comprises: I

an operating plunger for said valve means;

lever means pivotally mounted at a first end thereof adjacent said valvemeans and having reel means mounted on a second end thereof, saidlevermeans being constrained to engage and depress said plunger when pivoteddownwardly about said first end; disc means mounted for verticalmovement on said rod belowsaid float and being adapted to engage saidfloat in response to said second fluid level corresponding to a leakagecondition; and cable means connecting said disc means to said reel meanson said second end of saidlever means. 12. The invention of claim 11wherein one end of said cable means is wound about said reel means andsaid reel means is pivotally and adjustably mounted on said lever means,whereby said cable means may be selectively wound or unwound from saidreel means to adjust the position of said disc means on said rod means.

13. The invention of claim 12 wherein means are provided for lockingsaid reel means in selected positions.

14. The invention of claim 11, wherein means are provided for lockingsaid lever means in a fixed position.

15. An audible alarm device for detecting and signalling the advent ofan overflow or leakage condition in a fluid storage tank, comprising: I

a source of dry nitrogen gas under pressure;

gas operated audible means external of said storage tank;

pneumatic valve means mounted internally of said storage tank includingpneumatic pressure lines interconnecting opposite sides of said valvemeans with said sourceand said audible means, respectively; and

float means mounted internally of said storage tank,

interconnected with said valve means, and responsive to'p redete'rminedfluid levels representing the advent of an overflow or leakage conditionin said storage tank to actuate said valve means to transmit gas fromsaid source through said pneumatic lines to sound said'audible means.

16. The invention defined in claim l5 wherein said float meanscomprises:

a float in said tank mounted for slidable movement on vertical rod meansin response to varying fluid levels in said tank;

first and second linkage means extending from said rod means to saidvalve means for actuating said valve means, said float rising along saidrod means and engaging said first linkage meansto actuate said valvemeans and sound said audible means in response to a first fluid levercorresponding to an overflow condition in said tank, said float movingdown said rod means and engaging said second linkage means to actuatesaidvalve means. and sound said audible means in response to a secondfluid level corresponding to a leakage condition in saidtank.

17. The invention defined in claim 16, wherein said valve means isnormally closed and said first linkage means comprises: I

pivot means on said valve means;

an operating plunger for said valve means; and

a bell crank lever pivoted intermediate the ends thereof on said pivotmeans; said bell crank lever having means for engaging said float on oneend thereof and means engaging said operating plunger on the other endthereof.

' 18. The invention according to claim 16 wherein said valve means isnormally closed and said second linkage means comprises:

an operating plunger for said valve means 1 lever means pivotallymounted at a first end thereof adjacent said valve means and having reelmeans mounted on a second end thereof, said lever means beingconstrained to engage and depress said plunger when pivoted downwardlyabout said first end; disc means mounted for vertical movement on saidrod below said float and being adapted to engage said float in responseto said second fluid level corresponding to a leakage condition; andcable means connecting said disc means to said reel lectively wound orunwound from said disc means to adjust the position thereof on said rodmeans.

20. The invention of claim 1-9 wherein means are pro- I vided forlocking said reel means in selected positions.

21. The invention of claim 18 wherein means are provided for lockingsaid lever means in a fixed position.

1. An audible alarm device for detecting and signalling the advent of anoverflow condition in a fluid storage tank, comprising: a source of drynitrogen gas under pressure; gas operated audible means external of saidstorage tank; valve means mounted internally of said storage tankincluding pneumatic pressure lines interconnecting opposite sides ofsaid valve means with said source and said audible means, respectively;and float means mounted internally of said storage tank, interconnectedwith said valve means, and responsive to a predetermined fluid levelrepresenting the advent of an overflow condition in said storage tank toactuate said valve means to transmit gas from said source through saidpneumatic lines to said audible means, said float means including afloat in said tank, a fluid pervious float cage containing said floatand constraining the same to a limited vertical displacement in responseto varying fluid levels in said tank, and linkage means extending fromsaid float cage to said valve means for actuating said valve means, saidfloat rising in said float cage and engaging said linkage means inresponse to said predetermined fluid level to constrain said linkagemeans to actuate said valve means and effect actuation of said audiblemeans; pivot means on said valve means; an operating plunger for saidvalve means; and a bell crank lever pivoted intermediate the endsthereof on said pivot means; said bell crank lever being rigidly affixedto said float on one end thereof and means engaging said operatingplunger on the other end thereof.
 2. The invention defined in claim 1including filter means connected between said source of dry nitrogen gasand said pneumatic pressure lines for filtering out foreign materialsfrom said nitrogen gas.
 3. A system for detecting and signaling theadvent of oil spills by a ship or barge having at least one oil tankthereon comprising: a. an alarm device including a source of drynitrogen gas under pressure, gas operated audible means exernal of saidstorage tank, pneumatic valve means mounted internally of said storagetank including pneumatic pressure lines interconnecting opposite sidesof said valve means with said source and said audible means,respectively, and float means interconnected with said valve means, andresponsive to predetermined fluid levels to actuate said valve means totransmit gas from said source through said pneumatic lines to sound saidaudible means; b. means for mounting at least one of said alarm devicesin said at least one tank to constrain said float means to actuate saidvalve means To transmit gas from said source through said pneumaticlines to said audible means in response to at least one predeterminedfluid level in said at least one tank, and c. means for mounting atleast one of said alarm devices in the bilge or rakes of said ship orbarge, respectively, to constrain said float means to actuate said valvemeans in response to a sinking condition of said ship or barge.
 4. Theinvention of claim 3 wherein one of said predetermined fluid levels insaid tank corresponds to an overflow condition in said tank and saidaudible means is sounded in response to said overflow condition.
 5. Theinvention of claim 3 wherein one of said predetermined fluid levels insaid tank corresponds to a leakage condition in said tank and saidaudible means is sounded in response to said leakage condition.
 6. Theinvention of claim 3 wherein a first predetermined fluid level in saidtank corresponding to an overflow condition will sound said audiblemeans and a second predetermined fluid level in said tank correspondingto a leakage condition will also sound said audible means.
 7. Theinvention defined in claim 3, wherein said float means comprises: afloat in said tank; a fluid pervious float cage containing said floatand constraining same to a limited vertical displacement in response tovarying fluid levels in said tank; and linkage means extending from saidfloat cage to said valve means for actuating said valve means, saidfloat rising in said float cage and engaging said linkage means inresponse to said predetermined fluid level to constrain said linkagemeans to actuate said valve means and effect the sounding of saidaudible means.
 8. The invention defined in claim 7, wherein said valvemeans is normally closed and said linkage means comprises: pivot meanson said valve means: an operating plunger for said valve means; and abell crank lever pivoted intermediate the ends thereof on said pivotmeans; said bell crank lever being rigidly affixed to said float on oneend thereof and means engaging said operating plunger on the other endthereof.
 9. The invention of claim 3 wherein said float means comprises:a float in said tank mounted for slidable movement on vertical rod meansin response to varying fluid levels in said tank; first and secondlinkage means extending from said rod means to said valve means foractuating said valve means, said float rising along said rod means andengaging said first linkage means to actuate said valve means and soundsaid audible means in response to a first fluid level corresponding toan overflow condition in said tank, said float moving down said rodmeans and engaging said second linkage means to actuate said valve meansand sound said audible means in response to a second fluid levelcorresponding to a leakage condition in said tank.
 10. The invention ofclaim 9 wherein said valve means is normally closed and said firstlinkage means comprises: pivot means on said valve means; an operatingplunger for said valve means; and a bell crank lever pivotedintermediate the ends thereof on said pivot means; said bell crank leverhaving means for engaging said float on one end thereof and meansengaging said operating plunger on the other end thereof.
 11. Theinvention of claim 9 wherein said valve means is normally closed andsaid second linkage means comprises: an operating plunger for said valvemeans; lever means pivotally mounted at a first end thereof adjacentsaid valve means and having reel means mounted on a second end thereof,said lever means being constrained to engage and depress said plungerwhen pivoted downwardly about said first end; disc means mounted forvertical movement on said rod below said float and being adapted toengage said float in response to said second fluid level correspondingto a leakage condition; and cable means connecting said disc means tosaid reel means on said second end of said lEver means.
 12. Theinvention of claim 11 wherein one end of said cable means is wound aboutsaid reel means and said reel means is pivotally and adjustably mountedon said lever means, whereby said cable means may be selectively woundor unwound from said reel means to adjust the position of said discmeans on said rod means.
 13. The invention of claim 12 wherein means areprovided for locking said reel means in selected positions.
 14. Theinvention of claim 11, wherein means are provided for locking said levermeans in a fixed position.
 15. An audible alarm device for detecting andsignalling the advent of an overflow or leakage condition in a fluidstorage tank, comprising: a source of dry nitrogen gas under pressure;gas operated audible means external of said storage tank; pneumaticvalve means mounted internally of said storage tank including pneumaticpressure lines interconnecting opposite sides of said valve means withsaid source and said audible means, respectively; and float meansmounted internally of said storage tank, interconnected with said valvemeans, and responsive to predetermined fluid levels representing theadvent of an overflow or leakage condition in said storage tank toactuate said valve means to transmit gas from said source through saidpneumatic lines to sound said audible means.
 16. The invention definedin claim 15 wherein said float means comprises: a float in said tankmounted for slidable movement on vertical rod means in response tovarying fluid levels in said tank; first and second linkage meansextending from said rod means to said valve means for actuating saidvalve means, said float rising along said rod means and engaging saidfirst linkage means to actuate said valve means and sound said audiblemeans in response to a first fluid lever corresponding to an overflowcondition in said tank, said float moving down said rod means andengaging said second linkage means to actuate said valve means and soundsaid audible means in response to a second fluid level corresponding toa leakage condition in said tank.
 17. The invention defined in claim 16,wherein said valve means is normally closed and said first linkage meanscomprises: pivot means on said valve means; an operating plunger forsaid valve means; and a bell crank lever pivoted intermediate the endsthereof on said pivot means; said bell crank lever having means forengaging said float on one end thereof and means engaging said operatingplunger on the other end thereof.
 18. The invention according to claim16 wherein said valve means is normally closed and said second linkagemeans comprises: an operating plunger for said valve means; lever meanspivotally mounted at a first end thereof adjacent said valve means andhaving reel means mounted on a second end thereof, said lever meansbeing constrained to engage and depress said plunger when pivoteddownwardly about said first end; disc means mounted for verticalmovement on said rod below said float and being adapted to engage saidfloat in response to said second fluid level corresponding to a leakagecondition; and cable means connecting said disc means to said reel meanson said second end of said lever means.
 19. The invention of claim 18wherein one end of said cable means is wound about said reel means andsaid reel means is pivotally and adjustably mounted on said lever means,whereby said cable means may be selectively wound or unwound from saiddisc means to adjust the position thereof on said rod means.
 20. Theinvention of claim 19 wherein means are provided for locking said reelmeans in selected positions.
 21. The invention of claim 18 wherein meansare provided for locking said lever means in a fixed position.